Various feed, dosing and metering pumps are known for delivering chemical additives to a supply of water or other liquid. Such pumps are particularly useful in fluid content monitors for adding reagents to test drinking, wastewater, and industrial water supplies for the presence of residual chlorine and other constituents. Conventionally, such monitoring has been performed using colorimetric reagent technology wherein a chemical reagent, such as DPD (N,N-diethyl-p-phenylenediamine), is dispensed into a test sample of water contained in a cuvette. The sample turns a certain hue, which depends upon the concentration of the chlorine in the water. This concentration is then photometrically determined by analyzing the hue with an appropriate electronic tester.
In order to obtain accurate test results, precisely measured amounts of reagent must be added to the test sample. Preferably, the reagents include an indicator chemical, such as DPD, and a buffer for adjusting the PH of the test sample. If the amounts of these reagents are not accurately controlled, erroneous measurements are likely to be taken. A dirty or damaged cuvette can also cause erroneous measurements.
What is still desired is a new and improved fluid content monitor that reliably and automatically delivers precisely measured doses of reagents to a water sample so that the sample may be accurately tested for the presence of selected constituent elements such as chlorine.